Optimizing in-order delivery of data packets during wireless communication handover

ABSTRACT

Systems and methodologies are described that facilitate processing service data units (SDU) in-order during communication handover in wireless networks. In particular, for mobile devices using re-transmission schemes, SDUs can be processed in-order by indicating to a target base station an index of a last SDU received in-order before handing off communication to the target base station. Additionally, SDUs received subsequent to one or more non-acknowledged SDUs can be forwarded to the target base station. Utilizing this information, the target base station can determine one or more SDUs the mobile device is preparing to re-transmit and can wait for this SDU before processing subsequently received SDUs. Also, a timer can be utilized to end a waiting period for the SDU.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patentapplication Ser. No. 60/955,607 entitled “METHOD AND APPARATUS FOROPTIMIZING IN-ORDER DELIVERY OF UPLINK PACKETS DURING HANDOFF INCOMMUNICATION SYSTEMS” which was filed Aug. 13, 2007. The entirety ofthe aforementioned application is herein incorporated by reference.

BACKGROUND

I. Field

The following description relates generally to wireless communications,and more particularly to delivering sequenced service data units (SDU)to wireless communication devices.

II. Background

Wireless communication systems are widely deployed to provide varioustypes of communication content such as, for example, voice, data, and soon. Typical wireless communication systems may be multiple-accesssystems capable of supporting communication with multiple users bysharing available system resources (e.g., bandwidth, transmit power, . .. ). Examples of such multiple-access systems may include code divisionmultiple access (CDMA) systems, time division multiple access (TDMA)systems, frequency division multiple access (FDMA) systems, orthogonalfrequency division multiple access (OFDMA) systems, and the like.Additionally, the systems can conform to specifications such as thirdgeneration partnership project (3GPP), 3GPP long term evolution (LTE),ultra mobile broadband (UMB), etc.

Generally, wireless multiple-access communication systems maysimultaneously support communication for multiple mobile devices. Eachmobile device may communicate with one or more base stations viatransmissions on forward and reverse links. The forward link (ordownlink) refers to the communication link from base stations to mobiledevices, and the reverse link (or uplink) refers to the communicationlink from mobile devices to base stations. Further, communicationsbetween mobile devices and base stations may be established viasingle-input single-output (SISO) systems, multiple-input single-output(MISO) systems, multiple-input multiple-output (MIMO) systems, and soforth. In addition, mobile devices can communicate with other mobiledevices (and/or base stations with other base stations) in peer-to-peerwireless network configurations.

MIMO systems commonly employ multiple (N_(T)) transmit antennas andmultiple (N_(R)) receive antennas for data transmission. The antennascan relate to both base stations and mobile devices, in one example,allowing bi-directional communication between the devices on thewireless network. Mobile devices can travel about one or more wirelessnetwork service areas. To facilitate service access while moving, mobiledevices can handover communications from one base station to anotherwhen moving within a specific range of the target base station. For thepurpose of this description a handover may refer to a hand over of acommunication from a base station to another base station as well as ahand over from and to the same base station. Further, the hand over maybe initiated by the network or by the mobile terminal. The handover mayalso occur in order to support mobility of users in the wireless system,or to provide balancing of load, or to facilitate variousreconfigurations of the connection or to facilitate handling ofunforeseeable error cases. Additionally, mobile devices can employre-transmission schemes, such as hybrid automatic repeat request (HARQ),to replicate delivery of data ensuring a higher probability ofsuccessful receipt.

In this regard, data packets can be delivered from a mobile device to abase station out-of-order, as a HARQ process re-transmits unsuccessfulpackets while it also continues to transmit new packets. Data packetscan be re-ordered by an appropriate protocol following potentiallyunordered delivery. However, when communications are handed over from asource to a target base station, the sequencing of the packets by theappropriate protocol is facilitated at the target base station byproviding information to the target base station about the sequencenumber of the first packet to expect.

SUMMARY

The following presents a simplified summary of one or more embodimentsin-order to provide a basic understanding of such embodiments. Thissummary is not an extensive overview of all contemplated embodiments,and is intended to neither identify key or critical elements of allembodiments nor delineate the scope of any or all embodiments. Its solepurpose is to present some concepts of one or more embodiments in asimplified form as a prelude to the more detailed description that ispresented later.

In accordance with one or more embodiments and corresponding disclosurethereof, various aspects are described in connection with facilitatingdetermining a last consecutive packet received by a source base stationand corresponding first missing packet before a handover. In particular,the target base station can receive packets following the lastconsecutive packet and an identifier of the last packet received anddelivered in-order by the source base station. The identifier can betransmitted from the source base station or mobile device handing-overcommunication. Thus, if there are missing packet sequence numbersbetween the last packet received by the source base station anddelivered in-order and the subsequent packets received, this canindicate an outstanding packet. The target base station can thus awaittransmission of the missing packet by the mobile device before orderingand analyzing the packets. In this regard, the target base station, uponreceiving subsequent packets from the source base station, is notifiedof the missing packets, and waits to order and decode the packets untilrelevant packets are received or timed out.

According to related aspects, a method for ordering data packets duringhandover in wireless communication networks is provided. The handovermay be network-initiated or terminal-initiated. The method can comprisereceiving an index of a last service data unit (SDU) received in-orderby a base station and obtaining one or more subsequent SDUs received bythe base station. The method can further include determining one or moremissing SDUs numbered between the index of the last SDU receivedin-order and the last of the one or more subsequent SDUs. Similarly themethod can further include determining one or more missing SDUs numberedbetween, and including, the index of the first missing SDU in thereceived set of packets and the last of the one or more subsequent SDUs.

Another aspect relates to a wireless communications apparatus. Thewireless communications apparatus can include at least one processorconfigured to receive a command for handing over communication of amobile device from a source base station and determine one or moreservice data units (SDU) that are to be re-transmitted following handingover communication. The at least one processor is further configured towait for the mobile device to transmit the one or more SDUs to bere-transmitted before expiration. The amount of time to wait may bebased upon a timer or observed received sequence numbers. In oneembodiment if received sequence number is larger than sequence number ofmissing packet, the at least one processor may stop waiting of a waittimer. The wireless communications apparatus can also include a memorycoupled to the at least one processor.

Yet another aspect relates to a wireless communications apparatus thatfacilitates processing data packets in-order upon handover in wirelesscommunications networks. The wireless communications apparatus cancomprise means for receiving a sequence index of a last service dataunit (SDU) received in-order at a source base station. The wirelesscommunications apparatus can additionally include means for determiningone or more SDUs to be re-transmitted by a related mobile device basedat least in part on the sequence index. Such retransmissions may bereferred to as selective retransmissions.

Still another aspect relates to a computer program product, which canhave a computer-readable medium including code for causing at least onecomputer to receive an index of a last SDU received in-order by an basestation. The computer-readable medium can also comprise code for causingthe at least one computer to receive one or more subsequent SDUsreceived by the base station. Moreover, the computer-readable medium cancomprise code for causing the at least one computer to determine one ormore missing SDUs numbered between the index of the last SDU receivedin-order and the earliest of the one or more subsequent SDUs.

According to a further aspect, a method for facilitating in-orderdelivery of data packets in wireless communication handover ispresented. The method can include receiving at a mobile device ahandover command for transferring communications to a target basestation. Or the method can include the mobile device making anautonomous decision for a handover to a target base station.Independently of the trigger for the handover, the method canadditionally include determining a sequence index of a last SDU receivedin-order from the mobile device and transmitting the sequence index tothe target base station in response to a handover.

Another aspect relates to a wireless communications apparatus. Thewireless communications apparatus can include at least one processorconfigured to issue a command for a handover of mobile devicecommunications to a disparate wireless communications apparatus. The atleast one processor can be further configured to obtain an index of alast SDU received in-order by the source base station from the mobiledevice. The index may be transmitted from a source base station to atarget base station over a dedicated interface between the basestations, such as, for example, the X2 interface in 3GPP systems, or viathe S1 interface if the X2 is not present. Another aspect relates to awireless communication apparatus that can include at least one processorconfigured to identify the index of a last SDU received in-order from amobile device as well as a list of SDUs received out of sequence from amobile device. The at least one processor may be configured to transmitthe index and out-of-sequence SDUs to a target base station over an X2,S1, or similar interface between base stations. The wirelesscommunications apparatus can also include a memory coupled to the atleast one processor.

Yet another aspect relates to a wireless communications apparatus forordered processing of data packets during handover in wirelesscommunication networks. The wireless communications apparatus cancomprise means for determining a sequence index of a last service dataunit (SDU) received in-order from a mobile device. The wirelesscommunications apparatus can additionally include means for transmittingthe sequence index to a disparate wireless communications apparatus inpreparation or in response to the occurrence of a handover commandrelated to the mobile device.

Still another aspect relates to a computer program product, which canhave a computer-readable medium including code for causing at least onecomputer to receive a handover command related to a mobile device fortransferring communications to a target base station. Thecomputer-readable medium can also comprise code for causing the at leastone computer to determine a sequence index of a last service data unit(SDU) received in-order from the mobile device. Moreover, thecomputer-readable medium can comprise code for causing the at least onecomputer to transmit the sequence index to the target base station inresponse to the handover command.

To accomplish the foregoing and related ends, the one or moreembodiments comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative aspects ofthe one or more embodiments. These aspects are indicative, however, ofbut a few of the various ways in which the principles of variousembodiments may be employed and the described embodiments are intendedto include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a wireless communication system inaccordance with various aspects set forth herein.

FIG. 2 is an illustration of an example communications apparatus foremployment within a wireless communications environment.

FIG. 3 is an illustration of an example wireless communications systemthat effectuates in-order processing of service data units (SDU) duringhandover.

FIG. 4 is an illustration of an example wireless communication systemthat displays sample message passing to process SDUs in-order duringhandover.

FIG. 5 is an illustration of an example methodology that facilitatesdetermining SDUs that are to be re-transmitted by a mobile device.

FIG. 6 is an illustration of an example methodology that facilitatestransmitting data to a target base station on handover indicating thelast SDU received in-order.

FIG. 7 is an illustration of an example mobile device that facilitatestransmitting an index of the last SDU received in-order.

FIG. 8 is an illustration of an example system that determines the lastSDU received in-order for processing of the SDUs.

FIG. 9 is an illustration of an example wireless network environmentthat can be employed in conjunction with the various systems and methodsdescribed herein.

FIG. 10 is an illustration of an example system that determines one ormore missing SDUs upon communication handover.

FIG. 11 is an illustration of an example system that transmits datarelated to one or more SDUs in a re-transmit queue for in-orderprocessing upon handover.

DETAILED DESCRIPTION

Various embodiments are now described with reference to the drawings,wherein like reference numerals are used to refer to like elementsthroughout. In the following description, for purposes of explanation,numerous specific details are set forth in-order to provide a thoroughunderstanding of one or more embodiments. It may be evident, however,that such embodiment(s) can be practiced without these specific details.In other instances, well-known structures and devices are shown in blockdiagram form in-order to facilitate describing one or more embodiments.

As used in this application, the terms “component,” “module,” “system,”and the like are intended to refer to a computer-related entity, eitherhardware, firmware, a combination of hardware and software, software, orsoftware in execution. For example, a component can be, but is notlimited to being, a process running on a processor, a processor, anobject, an executable, a thread of execution, a program, and/or acomputer. By way of illustration, both an application running on acomputing device and the computing device can be a component. One ormore components can reside within a process and/or thread of executionand a component can be localized on one computer and/or distributedbetween two or more computers. In addition, these components can executefrom various computer readable media having various data structuresstored thereon. The components can communicate by way of local and/orremote processes such as in accordance with a signal having one or moredata packets (e.g., data from one component interacting with anothercomponent in a local system, distributed system, and/or across a networksuch as the Internet with other systems by way of the signal).

Furthermore, various embodiments are described herein in connection witha mobile device. A mobile device can also be called a system, subscriberunit, subscriber station, mobile station, mobile, remote station, remoteterminal, access terminal, user terminal, terminal, wirelesscommunication device, user agent, user device, or user equipment (UE). Amobile device can be a cellular telephone, a cordless telephone, aSession Initiation Protocol (SIP) phone, a wireless local loop (WLL)station, a personal digital assistant (PDA), a handheld device havingwireless connection capability, computing device, or other processingdevice connected to a wireless modem. Moreover, various embodiments aredescribed herein in connection with a base station. A base station canbe utilized for communicating with mobile device(s) and can also bereferred to as an access point, Node B, evolved Node B (eNode B or eNB),base transceiver station (BTS), home NodeB, home evolved Node B,wireless router or some other terminology.

Moreover, various aspects or features described herein can beimplemented as a method, apparatus, or article of manufacture usingstandard programming and/or engineering techniques. The term “article ofmanufacture” as used herein is intended to encompass a computer programaccessible from any computer-readable device, carrier, or media. Forexample, computer-readable media can include but are not limited tomagnetic storage devices (e.g., hard disk, floppy disk, magnetic strips,etc.), optical disks (e.g., compact disk (CD), digital versatile disk(DVD), etc.), smart cards, and flash memory devices (e.g., EPROM, card,stick, key drive, etc.). Additionally, various storage media describedherein can represent one or more devices and/or other machine-readablemedia for storing information. The term “machine-readable medium” caninclude, without being limited to, wireless channels and various othermedia capable of storing, containing, and/or carrying instruction(s)and/or data.

The techniques described herein may be used for various wirelesscommunication systems such as code division multiple access (CDMA), timedivision multiple access (TDMA), frequency division multiple access(FDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency domain multiplexing (SC-FDMA) and other systems. Theterms “system” and “network” are often used interchangeably. A CDMAsystem may implement a radio technology such as Universal TerrestrialRadio Access (UTRA), CDMA2000, etc. UTRA includes Wideband-CDMA (W-CDMA)and other variants of CDMA. CDMA2000 covers IS-2000, IS-95 and IS-856standards. A TDMA system may implement a radio technology such as GlobalSystem for Mobile Communications (GSM). An OFDMA system may implement aradio technology such as Evolved UTRA (E-UTRA), Ultra Mobile Broadband(UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20,Flash-OFDM, etc. UTRA and E-UTRA are part of Universal MobileTelecommunication System (UMTS). 3GPP Long Term Evolution (LTE) is anupcoming release that uses E-UTRA, which employs OFDMA on the downlinkand SC-FDMA on the uplink. UTRA, E-UTRA, UMTS, LTE and GSM are describedin documents from an organization named “3rd Generation PartnershipProject” (3GPP). CDMA2000 and UMB are described in documents from anorganization named “3rd Generation Partnership Project 2” (3GPP2).

Referring now to FIG. 1, a wireless communication system 100 isillustrated in accordance with various embodiments presented herein.System 100 comprises a base station 102 that can include multipleantenna groups. For example, one antenna group can include antennas 104and 106, another group can comprise antennas 108 and 110, and anadditional group can include antennas 112 and 114. Two antennas areillustrated for each antenna group; however, more or fewer antennas canbe utilized for each group. Base station 102 can additionally include atransmitter chain and a receiver chain, each of which can in turncomprise a plurality of components associated with signal transmissionand reception (e.g., processors, modulators, multiplexers, demodulators,demultiplexers, antennas, etc.), as will be appreciated by one skilledin the art.

Base station 102 can communicate with one or more mobile devices such asmobile device 116 and mobile device 122; however, it is to beappreciated that base station 102 can communicate with substantially anynumber of mobile devices similar to mobile devices 116 and 122. Mobiledevices 116 and 122 can be, for example, cellular phones, smart phones,laptops, handheld communication devices, handheld computing devices,satellite radios, global positioning systems, PDAs, and/or any othersuitable device for communicating over wireless communication system100. As depicted, mobile device 116 is in communication with antennas112 and 114, where antennas 112 and 114 transmit information to mobiledevice 116 over a forward link 118 and receive information from mobiledevice 116 over a reverse link 120. Moreover, mobile device 122 is incommunication with antennas 104 and 106, where antennas 104 and 106transmit information to mobile device 122 over a forward link 124 andreceive information from mobile device 122 over a reverse link 126. In afrequency division duplex (FDD) system, forward link 118 can utilize adifferent frequency band than that used by reverse link 120, and forwardlink 124 can employ a different frequency band than that employed byreverse link 126, for example. Further, in a time division duplex (TDD)system, forward link 118 and reverse link 120 can utilize a commonfrequency band and forward link 124 and reverse link 126 can utilize acommon frequency band.

Each group of antennas and/or the area in which they are designated tocommunicate can be referred to as a sector of base station 102. Forexample, antenna groups can be designed to communicate to mobile devicesin a sector of the areas covered by base station 102. In communicationover forward links 118 and 124, the transmitting antennas of basestation 102 can utilize beamforming to improve signal-to-noise ratio offorward links 118 and 124 for mobile devices 116 and 122. Also, whilebase station 102 utilizes beamforming to transmit to mobile devices 116and 122 scattered randomly through an associated coverage, mobiledevices in neighboring cells can be subject to less interference ascompared to a base station transmitting through a single antenna to allits mobile devices. Moreover, mobile devices 116 and 122 can communicatedirectly with one another using a peer-to-peer or ad hoc technology asdepicted.

According to an example, system 100 can be a multiple-inputmultiple-output (MIMO) communication system. Further, system 100 canutilize substantially any type of duplexing technique to dividecommunication channels (e.g., forward link, reverse link) such as FDD,TDD, and the like. In one example, the mobile devices 116/122 cancommunicate with the base station 102 using a re-transmission scheme,such as hybrid automatic repeat request (HARQ), such that the mobiledevices 116/122 can re-transmit service data units (SDU) that are notsuccessfully received by the base station 102. For example, the basestation 102 can transmit an acknowledgement (ACK) and/or non-ACK tonotify the mobile device 116/122 of the receive status for the SDUs. There-transmission scheme can, thus, re-transmit SDUs after subsequentlyindexed SDUs are received by the base station 102 where the base station102 previously responded to receiving the re-transmit SDUs with anon-ACK. In this regard, when the correct SDUs are received afterpossible re-transmission, the base station 102 can order the SDUsaccording to a specified sequence number.

Moreover, the mobile devices 116/122 can communicate with the basestation 102 while traveling in a geographic region. Upon moving within agiven proximity of a target base station (not shown), mobile devices116/122 can handover communication from the source base station 102 tothe target base station. In one example, the source base station 102 cansend a non-ACK in response to SDU transmission by a mobile device 116and/or 122, which can mark the SDU for re-transmission. Beforere-transmission, the mobile device 116 and/or 122 can transmit asubsequently indexed SDU to the base station 102 that can besuccessfully received (e.g., the source base station 102 transmits anACK back to the device). Further in this example, the mobile device 116and/or 122 can initiate a handover to the target base station, leavingan SDU in its re-transmission queue though a subsequent SDU was receivedby the source base station 102.

In this example, the target base station can receive an indication ofthe last SDU received and delivered in-order, which is the SDU beforethe one in the re-transmission queue in this example. Also, the targetbase station can receive the subsequently received SDU from the sourcebase station 102. Thus, the target base station can determine, based onthe index and the first received SDU, that an SDU is outstanding, andthe target base station can await re-transmission of the SDU by themobile device 116 and/or 122. It is to be appreciated that the index ofthe last SDU received and delivered in-order can be transmitted to thetarget base station by the source base station 102 and/or the mobiledevice 116 and/or 122 upon handover, in one example.

Turning to FIG. 2, illustrated is a communications apparatus 200 foremployment within a wireless communications environment. Thecommunications apparatus 200 can be a base station or a portion thereof,a mobile device or a portion thereof, or substantially anycommunications apparatus that receives data transmitted in a wirelesscommunications environment. The communications apparatus 200 can includea last SDU index determiner 202 that obtains the index or sequencenumber of the last SDU received and delivered at the communicationprotocol of a mobile device or base station. The index may be determinedat the time of a handover at apparatus 200. The communication protocolmay be, for example, the E-UTRAN Radio Link Protocol (RLC as specified3GPP TS 36.322) or E-UTRAN Packet Data Convergence Protocol (PDCP asspecified in TS 36.323) or similar Internet Protocol adaptation layer.The communications apparatus 200 also includes an SDU receiver 204 thatreceives one or more SDUs from a mobile device or base station usedpreviously to handover to the communications apparatus 200, as well asan SDU reorderer 206 that arranges SDUs according to respective sequencenumbers for decoding data in the SDUs.

According to an example, the communications apparatus 200 can receive ahandover request from a disparate communications apparatus (e.g., asource base station) to receive a communication from a mobile device(not shown) currently communicating with a disparate communicationsapparatus (not shown). According to another example, the communicationsapparatus 200 can accept a mobile device that autonomously hands over tothe apparatus. Subsequent to either of the aforementioned events thecommunications apparatus 200 can also receive one or more SDUstransmitted by the mobile device to the disparate communicationsapparatus that were not processed by the disparate communicationsapparatus because a prior SDU was not yet successfully received. Thisprior SDU can be arranged for re-transmission by the mobile device, inthis example, following the handover. Thus, the disparate communicationsapparatus will not receive re-transmission of the prior SDU and can,thus, transmit its subsequent SDUs to the communications apparatus 200for processing.

The SDU receiver 204 can receive the one or more subsequent SDUs fromthe disparate communications apparatus. It will be appreciated that themobile device and/or another device can transmit the subsequent SDUs tothe communications apparatus 200 as well; moreover, the transmission canbe in response to a request from the communications apparatus 200 in oneexample. In an example, the communications apparatus 200 may requesttransmission of only the missing SDUs from the mobile terminal based onthe index of the last SDU received in sequence (or the index of thefirst missing SDU) as well as the one or more SDUs receivedout-of-sequence from the source base station. The communicationsapparatus 200 can compare the index obtained by the last SDU indexdeterminer 202 to the one or more subsequent SDUs received by the SDUreceiver 204 to determine whether the one or more subsequent SDUsreceived can be delivered to upper layers immediately or if there areone or more preceding SDUs in the re-transmission or HARQ queue of themobile device. This can be determined where sequence numbers are missingbetween the index and first subsequent SDU received. If such adiscrepancy exists, the communications apparatus 200 can await themobile device to re-transmit the prior SDU. Once the prior SDU(s) is/aretransmitted by the mobile device to the communications apparatus 200 (oronce a wait timer has expired in one example) such that thecommunications apparatus 200 has received sequenced SDUs, the SDUreorderer 206 can order the SDUs according to sequence allowing thecommunications apparatus 200 to deliver the SDUs to the upper layer insequence and without gaps in the sequence. If the wait timer expires,the communications apparatus 200 may deliver in sequence but with gaps.

Now referring to FIG. 3, illustrated is a wireless communications system300 that can sequence SDUs received and delivered out-of-order inwireless communication system, for instance, as may happen during ahandover or re-establishment of the lower protocol layers, or terminalinitiated mobility such as forward handover or radio link failurerecovery or handover failure recovery. Each wireless device 302 and 304can be a base station, mobile device, or portion thereof. In oneexample, wireless device 302 can transmit information to wireless device304 over a forward link or downlink channel; further wireless device 302can receive information from wireless device 304 over a reverse link oruplink channel. Moreover, system 300 can be a MIMO system, and thewireless devices 302 and 304 can communicate on a radio link control(RLC) layer that transforms service data into protocol data fortransmission over a protocol layer, such as PDCP. Also, the componentsand functionalities shown and described below in the wireless device 302can be present in the wireless device 304 as well and vice versa, in oneexample; the configuration depicted excludes these components for easeof explanation.

Wireless device 302 includes an SDU receiver 306 that can receive SDUsfrom wireless device 304 and/or other wireless devices (not shown), anSDU reorderer 308 that can sequentially arrange SDUs received out ofsequence, and an SDU wait timer 310 that can specify an amount of timeto await re-transmission of SDUs not received by the wireless device 304while in communication with a previous wireless device for which ahandover command is received. Wireless device 304 can include a last SDUindex determiner 312 that can obtain the index of a last SDU receivedand delivered in-order prior to a handover from the wireless device 304to the wireless device 302 as well as an SDU transmitter 314 that cantransmit SDUs received by the wireless device 304 for which one or moreprior indexed SDUs were not successfully received by the wireless device304. The SDU transmitter 314 is capable of forwarding SDUs over anetwork interface such as, for example, the aforementioned X2 interfaceor S1 interface. It will be appreciated that the transmitted SDUs can bestored at the wireless device 304 (e.g., in a buffer) while awaiting are-transmission of a missing sequence numbered SDU. Additionally, itwill be appreciated that missing sequence numbered SDUs need not be theresult of failed transmission; rather, in one example, paralleltransmission using multiple antennas, or multiple HARQ processes, can beutilized where SDUs can be received out of sequence due to independenttransmission.

According to an example, the wireless device 304 can communicate with amobile device (not shown) providing wireless access services thereto.The mobile device can communicate with the wireless device 304 usingHARQ, ARQ or other re-transmission scheme such that SDUs can bere-transmitted to the wireless device 304 following subsequently indexedSDUs to promote successful delivery of the SDUs. In one example, themobile device can request a handover to the wireless device 302, or thewireless device 304 can request a handover on behalf of the mobiledevice where one or more SDUs are in the re-transmit queue of the mobiledevice. Following the handover request, the wireless device 302 canbegin receiving SDUs from the mobile device.

In this case, however, where there is an outstanding SDU to bere-transmitted by the mobile device, the last SDU index determiner 312can transmit the index of the last SDU received and delivered in-orderto the wireless device 302. Additionally, where the mobile device hastransmitted additional SDUs indexed subsequent to the SDU to bere-transmitted, the SDU transmitter 314 can transmit the SDUs to thewireless device 302, which can receive the SDUs from a network interfacevia SDU receiver 306. The mobile device can be informed by SDU receiver306 about a missing SDU in need of retransmission based on the index ofthe last SDU received and the additional SDUs indexed subsequent to theSDU to be re-transmitted. When not informed, the mobile can retransmitall SDUs starting from the last known received in sequence by wirelessdevice 304. As there is an outstanding SDU in the re-transmit queue ofthe mobile device in this example, the SDU wait timer 310 can be set toestablish a time at which the wireless device 302 can determine there-transmit has timed out or that the wireless device 302 otherwise doesnot expect to receive the re-transmit SDU.

Once the wireless device 302 receives the SDU or the SDU wait timer 310expires, for example, the SDU reorderer 308 can arrange the SDUssequentially to interpret data within one or more SDUs and deliver anordered stream of packets to the upper layer, such as the internetprotocol (IP). In one example, the wireless device 302 can be an basestation in a wireless communications network, and the wireless device304 can be a disparate base station to which communication with a mobiledevice is handed over. In another example, the wireless device 304 canbe a mobile device handing over communication from a base station to thewireless device 302. Thus, the mobile device can transmit the index tothe wireless device 302 via the last SDU index determiner 312 as well assubsequent SDUs via the SDU transmitter 314, in one example.

Turning now to FIG. 4, illustrated is an example wireless communicationsnetwork 400 that facilitates in-order delivery of SDUs in wirelesscommunication handover. A mobile device 402 is provided thatcommunicates SDUs over a protocol layer (which can use a RLC or a PDCP,for example) to one or more base stations 406 and/or 412. In the exampledepicted, the mobile device 402 can communicate sequenced SDUs a, b, andc to base station 406. However, base station 406 receives only a and csuccessfully and transmits a negative-ACK for b, where the negativereceipt is indicated by the X. As described, mobile device 402 canutilize a re-transmission scheme, such that b can be stored in atransmit buffer 404 of the mobile device 402 for subsequentre-transmission. The base station 406 upon successfully receiving a andc can store a in an uplink receive buffer 410 or otherwise process SDUa. However, the base station 406 waits for b before processing c, andthus stores c in a receive buffer 408.

According to this example, before SDU b is successfully received by basestation 406 via re-transmission from mobile device 402, a handover ofmobile device 402 communication from base station 406 to base station412 occurs. As indicated, this can result when mobile device 402 comeswithin a specified proximity of base station 412 additional servicesoffered by the base station, re-selection by mobile terminal and/or thelike. Since mobile device 402 now communicates with base station 412,the re-transmission of SDU b will go to base station 412 since basestation 406 no longer processes SDUs from the mobile device 402.However, if base station 412 immediately begins processing SDUs frommobile device 402, it may receive re-transmitted SDUs out-of-order, andthe resulting SDUs may never be processed. Thus, the mobile device 402and/or base station 406 can determine the index of the last SDU receivedand delivered in-order, which is a in this case. In addition, basestation 406 may also indicate with appropriate signaling that sequencenumbers up to and including ‘a’ are received, and additionally that ‘c’is also received to facilitate the mobile terminal decision toretransmit only ‘b’, and then proceed with transmission of ‘d’.

Once determined, the index can be transmitted to the base station 412along with subsequently received SDUs, which includes SDU c in thisexample. The base station 412 can utilize this to determine that betweenthe index of SDU a and SDU c, SDU b has not been received. Thus, basestation 412 can await SDU b to be re-transmitted from the mobile device402. As shown, the mobile device 402 transmits SDU b along with a newSDU d to the base station 412. Upon receiving SDU b, the base station412 can order and process the SDUs b and c as well as newly acquired SDUd. In addition, as indicated by the arrow from base station 412 to basemobile device 402, base station 412 may indicate with appropriatesignaling that at least sequence numbers ‘a’ and ‘c’ are received. Thus,in-order delivery and processing of SDUs during handover ofcommunication is achieved as shown above.

Referring to FIGS. 5-6, methodologies relating to in-order processing ofSDUs during wireless communication handover are illustrated. While, forpurposes of simplicity of explanation, the methodologies are shown anddescribed as a series of acts, it is to be understood and appreciatedthat the methodologies are not limited by the order of acts, as someacts may, in accordance with one or more embodiments, occur in differentorders and/or concurrently with other acts from that shown and describedherein. For example, those skilled in the art will understand andappreciate that a methodology could alternatively be represented as aseries of interrelated states or events, such as in a state diagram.Moreover, not all illustrated acts may be required to implement amethodology in accordance with one or more embodiments.

Turning to FIG. 5, a methodology 500 that facilitates ordered processingof SDUs in wireless communication handover is displayed. At 502, anindex for the last SDU received in-order is received. In one example,this can be received from a source base station in response to ahandover command. The index identifies the last SDU received from amobile device where the mobile device has an outstanding SDU in itsre-transmit queue, for example. At 504, one or more missing SDUs aredetermined based at least in part on the index. As described, subsequentSDUs can be received; thus, missing SDUs can be determined by evaluatingthe received index along with indices of the subsequent SDUs received.

At 506, waiting occurs for delivery of the one or more missing SDUs. Inone example, since the missing SDUs are identified, waiting can occuruntil the mobile device transmits the missing SDUs from its re-transmitqueue. In another example, a timer can be utilized in the waiting suchthat upon expiration, received SDUs can be ordered and processed withouthaving received the missing SDUs. At 508, if the missing SDUs aredelivered, the SDUs are ordered and processed with the missing SDUs, assoon as they become available. In this regard, data included in the SDUscan be delivered to upper layers in-order, for example.

Turning to FIG. 6, illustrated is a methodology 600 that transmitsinformation during wireless device communication handover to facilitatein-order processing of SDUs. At 602, a handover indication is received;this can be from a mobile device or base station and can be in responseto a mobile device moving about a geographic region, for example. At604, the last SDU received in-order from the mobile device isdetermined. For example, a negative-ACK can be transmitted for areceived SDU such that the immediately preceding SDU that issuccessfully received is determined to be the last SDU receivedin-order. Alternatively, an ACK can be transmitted for all SDUspreceding. At 606, the index of the last SDU received in-order (or,alternatively, the index of first missing SDU) can be transmitted to abase station to facilitate handover of mobile device communication asdescribed previously. In addition, at 608, subsequently received SDUalong with its sequence number can be transmitted to the base stationfor handover as well. For example, the SDUs can be deciphered andheader-decompressed.

It will be appreciated that, in accordance with one or more aspectsdescribed herein, inferences can be made regarding determining SDUs tobe re-transmitted during or following handover as described. As usedherein, the term to “infer” or “inference” refers generally to theprocess of reasoning about or inferring states of the system,environment, and/or user from a set of observations as captured viaevents and/or data. Inference can be employed to identify a specificcontext or action, or can generate a probability distribution overstates, for example. The inference can be probabilistic—that is, thecomputation of a probability distribution over states of interest basedon a consideration of data and events. Inference can also refer totechniques employed for composing higher-level events from a set ofevents and/or data. Such inference results in the construction of newevents or actions from a set of observed events and/or stored eventdata, whether or not the events are correlated in close temporalproximity, and whether the events and data come from one or severalevent and data sources.

In one example, inferences can be made in determining whether there areSDUs outstanding in a mobile device re-transmit queue upon handing overcommunications. For example, different heuristics can be utilized inthis regard, and the proper heuristics can be inferred. In one example,as described, sequence numbers can be utilized to determine existence ornon-existence of an SDU. Additionally or alternatively, a time stamp canbe similarly utilized in this regard. Also, SDUs can be decoded todetermine if a previous SDU is needed for enhance or successful decodingin one example.

FIG. 7 is an illustration of a device 700 that facilitates determining alast SDU index received in-order. Device 700 comprises a receiver 702that receives a signal from, for instance, a receive antenna (notshown), performs typical actions on (e.g., filters, amplifies,downconverts, etc.) the received signal, and digitizes the conditionedsignal to obtain samples. Receiver 702 can comprise a demodulator 704that can demodulate received symbols and provide them to a processor 706for channel estimation. Processor 706 can be a processor dedicated toanalyzing information received by receiver 702 and/or generatinginformation for transmission by a transmitter 716, a processor thatcontrols one or more components of device 700, and/or a processor thatboth analyzes information received by receiver 702, generatesinformation for transmission by transmitter 716, and controls one ormore components of device 700.

Device 700 can additionally comprise memory 708 that is operativelycoupled to processor 706 and that can store data to be transmitted,received data, information related to available channels, dataassociated with analyzed signal and/or interference strength,information related to an assigned channel, power, rate, or the like,and any other suitable information for estimating a channel andcommunicating via the channel. Memory 708 can additionally storeprotocols and/or algorithms associated with estimating and/or utilizinga channel (e.g., performance based, capacity based, etc.).

It will be appreciated that the data store (e.g., memory 708) describedherein can be either volatile memory or nonvolatile memory, or caninclude both volatile and nonvolatile memory. By way of illustration,and not limitation, nonvolatile memory can include read only memory(ROM), programmable ROM (PROM), electrically programmable ROM (EPROM),electrically erasable PROM (EEPROM), or flash memory. Volatile memorycan include random access memory (RAM), which acts as external cachememory. By way of illustration and not limitation, RAM is available inmany forms such as synchronous RAM (SRAM), dynamic RAM (DRAM),synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhancedSDRAM (ESDRAM), Synchlink DRAM (SLDRAM), and direct Rambus RAM (DRRAM).The memory 708 of the subject systems and methods is intended tocomprise, without being limited to, these and any other suitable typesof memory.

Processor 706 and/or receiver 702 can further be operatively coupled toa last SDU index determiner 710 that can determine an index of an SDUsuccessfully received immediately prior to a non-acknowledged SDU. Theprocessor 706 can additionally be coupled to a re-transmit processor 712that can re-transmit SDUs which are not successfully received at an basestation (e.g., a non-ACK is received from the base station). There-transmit processor 712 can be a HARQ processor and/or the like.According to an example, the last SDU index determiner 710 can obtainthe index of the last SDU received in-order by evaluating a queue of there-transmit processor 712. If there is an SDU in the re-transmitprocessor 712 queue, the index of the last SDU received in-order can beone index unit subtracted from the index of the re-transmit SDU, forexample. Device 700 may further comprise a modulator 714 and transmitter716 that respectively modulate and transmit signal to, for instance, abase station, another device, etc. Although depicted as being separatefrom the processor 706, it will be appreciated that the last SDU indexdeterminer 710, re-transmit processor 712, demodulator 704, and/ormodulator 714 can be part of the processor 706 or multiple processors(not shown).

FIG. 8 is an illustration of a system 800 that facilitates ordering SDUsduring wireless communication handover using re-transmission. The system800 comprises a base station 802 (e.g., access point, . . . ) with areceiver 810 that receives signal(s) from one or more mobile devices 804through a plurality of receive antennas 806, and a transmitter 824 thattransmits to the one or more mobile devices 804 through a transmitantenna 808. Receiver 810 can receive information from receive antennas806 and is operatively associated with a demodulator 812 thatdemodulates received information. Demodulated symbols are analyzed by aprocessor 814 that can be similar to the processor described above withregard to FIG. 7, and which is coupled to a memory 816 that storesinformation related to estimating a signal (e.g., pilot) strength and/orinterference strength, data to be transmitted to or received from mobiledevice(s) 804 (or a disparate base station (not shown)), and/or anyother suitable information related to performing the various actions andfunctions set forth herein. Processor 814 is further coupled to a SDUreceiver 818 that receives SDUs from disparate base stations asdescribed above as well as mobile device(s) 804 upon communicationhandover to the base station. Processor 814 is further coupled to a SDUreorderer 820 that can arrange received SDUs from disparate basestations upon handover as well as mobile devices during re-transmission.

According to an example, one or more mobile devices 804 can handovercommunications to the base station 802 from a source base station (notshown). Upon handover, the mobile device(s) 804 can transmit SDUs on anRLC layer to the base station 802, which can be received by the SDUreceiver 818; however, as described herein, the mobile device(s) 804 canhave re-transmit SDUs in its queue from previous communication with thesource base station. In this regard, the mobile device(s) 804 and/or thesource base station can transmit an index for the last SDU received bythe source base station in-order (e.g., before the SDU in there-transmit queue). In addition, the source base station and/or mobiledevice(s) 804 can transmit subsequent SDUs to the base station 802. TheSDU receiver 818 can receive the subsequent SDUs as well as the index ofthe last SDU received in-order.

The base station 802 can then determine one or more SDUs missing betweenthe sequence starting with the index and ending with the firstsubsequent SDU. If SDUs are missing in this regard, the base station 802can wait for the mobile device(s) 804 to re-transmit the appropriateSDU, such as part of a HARQ re-transmission for example. In addition,the base station 802 can set a timer for receiving the missing SDU andcontinue without it if the timer expires. In either case, the SDUreorderer 820 can arrange the SDUs for processing thereof. Furthermore,although depicted as being separate from the processor 814, it is to beappreciated that the SDU receiver 818, SDU reorderer 820, demodulator812, and/or modulator 822 can be part of the processor 814 or multipleprocessors (not shown).

FIG. 9 shows an example wireless communication system 900. The wirelesscommunication system 900 depicts one base station 910 and one mobiledevice 950 for sake of brevity. However, it is to be appreciated thatsystem 900 can include more than one base station and/or more than onemobile device, wherein additional base stations and/or mobile devicescan be substantially similar or different from example base station 910and mobile device 950 described below. In addition, it is to beappreciated that base station 910 and/or mobile device 950 can employthe systems (FIGS. 1-3 and 7-8), configurations (FIG. 4), and/or methods(FIGS. 5-6) described herein to facilitate wireless communication therebetween.

At base station 910, traffic data for a number of data streams isprovided from a data source 912 to a transmit (TX) data processor 914.According to an example, each data stream can be transmitted over arespective antenna. TX data processor 914 formats, codes, andinterleaves the traffic data stream based on a particular coding schemeselected for that data stream to provide coded data.

The coded data for each data stream can be multiplexed with pilot datausing orthogonal frequency division multiplexing (OFDM) techniques.Additionally or alternatively, the pilot symbols can be frequencydivision multiplexed (FDM), time division multiplexed (TDM), or codedivision multiplexed (CDM). The pilot data is typically a known datapattern that is processed in a known manner and can be used at mobiledevice 950 to estimate channel response. The multiplexed pilot and codeddata for each data stream can be modulated (e.g., symbol mapped) basedon a particular modulation scheme (e.g., binary phase-shift keying(BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying(M-PSK), M-quadrature amplitude modulation (M-QAM), etc.) selected forthat data stream to provide modulation symbols. The data rate, coding,and modulation for each data stream can be determined by instructionsperformed or provided by processor 930.

The modulation symbols for the data streams can be provided to a TX MIMOprocessor 920, which can further process the modulation symbols (e.g.,for OFDM). TX MIMO processor 920 then provides N_(T) modulation symbolstreams to N_(T) transmitters (TMTR) 922 a through 922 t. In variousembodiments, TX MIMO processor 920 applies beamforming weights to thesymbols of the data streams and to the antenna from which the symbol isbeing transmitted.

Each transmitter 922 receives and processes a respective symbol streamto provide one or more analog signals, and further conditions (e.g.,amplifies, filters, and upconverts) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel.Further, N_(T) modulated signals from transmitters 922 a through 922 tare transmitted from N_(T) antennas 924 a through 924 t, respectively.

At mobile device 950, the transmitted modulated signals are received byN_(R) antennas 952 a through 952 r and the received signal from eachantenna 952 is provided to a respective receiver (RCVR) 954 a through954 r. Each receiver 954 conditions (e.g., filters, amplifies, anddownconverts) a respective signal, digitizes the conditioned signal toprovide samples, and further processes the samples to provide acorresponding “received” symbol stream.

An RX data processor 960 can receive and process the N_(R) receivedsymbol streams from N_(R) receivers 954 based on a particular receiverprocessing technique to provide N_(T) “detected” symbol streams. RX dataprocessor 960 can demodulate, deinterleave, and decode each detectedsymbol stream to recover the traffic data for the data stream. Theprocessing by RX data processor 960 is complementary to that performedby TX MIMO processor 920 and TX data processor 914 at base station 910.

A processor 970 can periodically determine which precoding matrix toutilize as discussed above. Further, processor 970 can formulate areverse link message comprising a matrix index portion and a rank valueportion.

The reverse link message can comprise various types of informationregarding the communication link and/or the received data stream. Thereverse link message can be processed by a TX data processor 938, whichalso receives traffic data for a number of data streams from a datasource 936, modulated by a modulator 980, conditioned by transmitters954 a through 954 r, and transmitted back to base station 910.

At base station 910, the modulated signals from mobile device 950 arereceived by antennas 924, conditioned by receivers 922, demodulated by ademodulator 940, and processed by a RX data processor 942 to extract thereverse link message transmitted by mobile device 950. Further,processor 930 can process the extracted message to determine whichprecoding matrix to use for determining the beamforming weights.

Processors 930 and 970 can direct (e.g., control, coordinate, manage,etc.) operation at base station 910 and mobile device 950, respectively.Respective processors 930 and 970 can be associated with memory 932 and972 that store program codes and data. Processors 930 and 970 can alsoperform computations to derive frequency and impulse response estimatesfor the uplink and downlink, respectively.

It is to be understood that the embodiments described herein can beimplemented in hardware, software, firmware, middleware, microcode, orany combination thereof. For a hardware implementation, the processingunits can be implemented within one or more application specificintegrated circuits (ASICs), digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs),field programmable gate arrays (FPGAs), processors, controllers,micro-controllers, microprocessors, other electronic units designed toperform the functions described herein, or a combination thereof.

When the embodiments are implemented in software, firmware, middlewareor microcode, program code or code segments, they can be stored in amachine-readable medium, such as a storage component. A code segment canrepresent a procedure, a function, a subprogram, a program, a routine, asubroutine, a module, a software package, a class, or any combination ofinstructions, data structures, or program statements. A code segment canbe coupled to another code segment or a hardware circuit by passingand/or receiving information, data, arguments, parameters, or memorycontents. Information, arguments, parameters, data, etc. can be passed,forwarded, or transmitted using any suitable means including memorysharing, message passing, token passing, network transmission, etc.

For a software implementation, the techniques described herein can beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. The software codes can be storedin memory units and executed by processors. The memory unit can beimplemented within the processor or external to the processor, in whichcase it can be communicatively coupled to the processor via variousmeans as is known in the art.

With reference to FIG. 10, illustrated is a system 1000 that determinesSDUs to be re-transmitted by a mobile device during wirelesscommunication handover. For example, system 1000 can reside at leastpartially within a base station, mobile device, etc. It is to beappreciated that system 1000 is represented as including functionalblocks, which can be functional blocks that represent functionsimplemented by a processor, software, or combination thereof (e.g.,firmware). System 1000 includes a logical grouping 1002 of electricalcomponents that can act in conjunction. For instance, logical grouping1002 can include an electrical component for receiving a sequence indexof a last SDU received in-order at a source base station 1004. Forexample, the index can relate to the last successfully received SDUwithout interruption (e.g., without requiring re-transmission), or theindex can be received by means of radio signaling. In addition, this canoccur during handover when a mobile device can be in the middle ofre-transmitting one or more SDUs. Further, logical grouping 1002 cancomprise an electrical component for determining one or more SDUs to bere-transmitted by a related mobile device based at least in part on thesequence index 1006. Thus, as described, the index can relate to thelast successfully received and processed SDU in sequence; thus, theindex combined with subsequent SDUs transmitted to the system 1000 canbe utilized to determine missing SDUs set for re-transmission in themobile device. Additionally, system 1000 can include a memory 1008 thatretains instructions for executing functions associated with electricalcomponents 1004 and 1006. While shown as being external to memory 1008,it is to be understood that one or more of electrical components 1004and 1006 can exist within memory 1008.

Turning to FIG. 11, illustrated is a system 1100 that transmits asequence index of a last SDU received in-order to facilitate sequentialprocessing of SDUs in a wireless communications network during handover.System 1100 can reside within a base station, mobile device, etc., forinstance. As depicted, system 1100 includes functional blocks that canrepresent functions implemented by a processor, software, or combinationthereof (e.g., firmware). System 1100 includes a logical grouping 1102of electrical components that facilitate transmitting relevantinformation to a target system for handover. Logical grouping 1102 caninclude an electrical component for determining a sequence index of alast SDU received in-order from a mobile device 1104. As described, thisis the last SDU received before a non-ACK is transmitted to the mobiledevice. This can be subsequently used, as described, to determine SDUsto be re-transmitted by the mobile device. Moreover, logical grouping1102 can include an electrical component for transmitting the sequenceindex to a disparate wireless communications apparatus in response to ahandover indication related to the mobile device 1106. Thus, uponreceiving a request for handover, the index can be determined to allowthe target system to determine which SDUs are to be expected from themobile device. Additionally, system 1100 can include a memory 1108 thatretains instructions for executing functions associated with electricalcomponents 1104 and 1106. While shown as being external to memory 1108,it is to be understood that electrical components 1104 and 1106 canexist within memory 1108.

What has been described above includes examples of one or moreembodiments. It is, of course, not possible to describe everyconceivable combination of components or methodologies for purposes ofdescribing the aforementioned embodiments, but one of ordinary skill inthe art may recognize that many further combinations and permutations ofvarious embodiments are possible. Accordingly, the described embodimentsare intended to embrace all such alterations, modifications andvariations that fall within the spirit and scope of the appended claims.Furthermore, to the extent that the term “includes” is used in eitherthe detailed description or the claims, such term is intended to beinclusive in a manner similar to the term “comprising” as “comprising”is interpreted when employed as a transitional word in a claim.

What is claimed is:
 1. A method of delivering data packets according tosequence numbers during handover at a target base station in wirelesscommunication networks, comprising: receiving, at the target basestation and from a source base station, signaling related to a firstmissing service data unit (SDU) following a last SDU received in-orderat the source base station from a related mobile device; obtaining, atthe target base station and from the source base station, one or moresubsequent SDUs received at the source base station; determining, at thetarget base station, one or more missing SDUs numbered between an indexof the last SDU received in-order and a highest index of the one or moresubsequent SDUs; and informing the related mobile device, by the targetbase station, of one or more missing SDUs based on a result of thedetermining.
 2. The method of claim 1, further comprising awaitingreception of the one or more missing SDUs and then delivering ordereddata packets to an upper layer.
 3. The method of claim 2, wherein saidawaiting reception is based at least in part on a wait timer.
 4. Themethod of claim 1, wherein the signaling related to the last SDUreceived in-order and the one or more subsequent SDUs are received fromthe source base station as part of a context transfer related to ahandover from the source base station for the related mobile device. 5.The method of claim 4, wherein the signaling related to the last SDUreceived in-order comprises the index of the last SDU received in-orderat the source base station.
 6. The method of claim 4, wherein thesignaling related to the last SDU received in-order comprises an indexof a first missing SDU among the packets received by the source basestation.
 7. The method of claim 4, further comprising receiving the oneor more missing SDUs as part of a re-transmission from the relatedmobile device.
 8. The method of claim 1, further comprising reorderingthe one or more subsequent SDUs with the one or more missing SDUs andinterpreting data within the one or more subsequent SDUs and the one ormore missing SDUs.
 9. The method of claim 1, wherein the signalingrelated to the last SDU received in-order is received from the relatedmobile device.
 10. The method of claim 1, wherein the signaling relatedto the last SDU received in-order is received from the source basestation.
 11. The method of claim 1, wherein the target base station andthe source base station are the same base station.
 12. The method ofclaim 1, wherein the handover is initiated by a wireless network overwhich the target and source base stations provide connectivity.
 13. Themethod of claim 1, wherein the handover is initiated by a mobileterminal.
 14. The method of claim 1, wherein the handover occurs tosupport user mobility in a wireless network over which the target andsource base station provide connectivity.
 15. The method of claim 1,wherein the handover occurs to support balancing of load from a wirelessnetwork over which the target and source base station provideconnectivity.
 16. The method of claim 1, wherein the handover occurs tofacilitate reconfiguration of a connection with the target and/or sourcebase station.
 17. The method of claim 1, wherein the handover occurs tofacilitate handling one or more errors in a wireless network over whichthe target and source base station provide connectivity.
 18. A wirelesscommunications apparatus, comprising: at least one processor configuredto: receive, at a target base station, a command for handing offcommunication of a mobile device from a source base station; receive, bythe target base station and from the source base station, an index of afirst missing service data unit (SDU) following a last SDU receivedin-order by the source base station from the mobile device; receive, atthe target base station and from the source base station, one or moresubsequent SDUs received by the source base station from the mobiledevice after failed receipt of the one or more SDUs to bere-transmitted; determine, at the target base station, one or moreservice data units (SDU) that are to be re-transmitted following handingoff communication; inform the mobile device, by the target base station,of one or more SDUs to be re-transmitted based on a result of thedetermining; and wait, at the target base station, for the mobile deviceto transmit the one or more SDUs to be re-transmitted before expirationof a wait timer; and a memory coupled to the at least one processor. 19.The wireless communications apparatus of claim 18, wherein the one ormore SDUs to be re-transmitted are determined, by the target basestation, at least in part by comparing the index of the last SDUreceived in-order to the one or more subsequent SDUs.
 20. The wirelesscommunications apparatus of claim 18, wherein the at least one processoris further configured to receive, at the target base station, the one ormore SDUs that are to be re-transmitted.
 21. The wireless communicationsapparatus of claim 20, wherein the at least one processor is furtherconfigured to reorder, at the target base station, the SDUs based atleast in part on the received re-transmitted SDUs.
 22. The wirelesscommunications apparatus of claim 21, wherein the at least one processeris further configured to process, at the target base station, thereordered SDUs to obtain related data.
 23. A wireless communicationsapparatus that facilitates processing data packets in-order uponhandover in wireless communications networks, comprising: means forreceiving, at a target base station and from a source base station, asequence index of a first missing service data unit (SDU) following alast SDU received in-order at the source base station from a relatedmobile device; means for receiving, at the target base station and fromthe source base station, one or more subsequent SDUs received at thesource base station; means for determining, at the target base station,one or more SDUs to be re-transmitted by the related mobile device basedat least in part on the sequence index; means for informing the relatedmobile device, by the target base station, of one or more SDUs to bere-transmitted based on a result of the determining.
 24. The wirelesscommunications apparatus of claim 23, further comprising means forreceiving, at the target base station, one or more subsequent SDUstransmitted by the mobile device following non-acknowledgement ofreceipt from the source base station for the one or more SDUs to bere-transmitted.
 25. The wireless communications apparatus of claim 23,wherein the one or more SDUs to be re-transmitted are determined, by thetarget base station, further based at least in part on a sequence indexof the one or more subsequent SDUs.
 26. The wireless communicationsapparatus of claim 23, wherein the sequence index is received, at thetarget base station, as part of a handover notification for the mobiledevice.
 27. The wireless communications apparatus of claim 26, whereinthe handover notification is generated by the mobile device once itmoves within proximity of the wireless communications apparatus.
 28. Thewireless communications apparatus of claim 23, further comprising meansfor receiving, at the target base station, the one or more SDUs to bere-transmitted from the mobile device.
 29. The wireless communicationsapparatus of claim 28, further comprising means for reordering andprocessing, at the target base station, one or more SDUs based at leastin part on the received re-transmitted SDUs.
 30. A computer programproduct, comprising: a non-transitory computer-readable mediumcomprising: code, executable at a target base station, for causing atleast one computer to receive signaling, from a source base station,related to a first missing service data unit (SDU) following a last SDUreceived in-order at the source base station from a related mobiledevice; code, executable at the target base station, for causing the atleast one computer to receive, from the source base station, one or moresubsequent SDUs received at the source base station; code, executable atthe target base station, for causing the at least one computer todetermine one or more missing SDUs numbered between an index of the lastSDU received in-order and a highest index of the one or more subsequentSDUs; and code, executable at the target base station, for informing therelated mobile device of one or more missing SDUs based on a result ofthe determining.
 31. The computer program product of claim 30, whereinthe computer-readable medium further comprises code, executable at thetarget base station, for causing the at least one computer to awaitreception of the one or more missing SDUs from the mobile device. 32.The computer program product of claim 31, wherein said awaitingreception is based at least in part on a wait timer.
 33. A method forfacilitating in-order processing of data packets in wirelesscommunication handover, comprising: receiving, by a source base station,a handover command related to a mobile device for transferringcommunications to a target base station; determining, by the source basestation, a sequence index of a first missing service data unit (SDU)following a last service data unit (SDU) received in-order from themobile device by the source base station; transmitting, by the sourcebase station, the sequence index to the target base station in responseto the handover command; transmitting, by the source base station, anon-acknowledgement in response to receiving one or more SDUs whosesequence index follows the last SDU received in-order from the mobiledevice; and forwarding, by the source base station and to the targetbase station, one or more subsequent SDUs indexed to follow sequentiallyfrom the one or more SDUs in response to which the non-acknowledgementis transmitted.
 34. A wireless communications apparatus, comprising: atleast one processor configured to: receive, by a source base station, acommand to handover mobile device communications to a a target basestation; obtain, by the source base station, an index of a first missingservice data unit (SDU) following a last SDU received in-order from themobile device; and transmit, by the source base station, the index tothe target base station to complete the handover; transmit, by thesource base station, a non-acknowledgement in response to receiving anSDU indexed subsequent the last SDU received in-order; transmit, by thesource base station and to the target base station, successfullyreceived SDUs indexed following the SDUs in response to which thenon-acknowledgement is transmitted; and a memory coupled to the at leastone processor.
 35. The wireless communications apparatus of claim 34,wherein the at least one processor is further configured to process thelast SDU received in-order.
 36. A wireless communications apparatus forordered processing of data packets during handover in wirelesscommunication networks, comprising: means for determining, by a sourcebase station, a sequence index of a first missing service data unit(SDU) following a last service data unit (SDU) received in-order from amobile device; means for transmitting, by the source base station, thesequence index to a target base station in response to a handovercommand related to the mobile device; means for transmitting, by thesource base station, a non-acknowledgement in response to receiving anSDU sequenced after the last SDU received in-order; means for receiving,by the source base station and from the mobile device, subsequent SDUssuccessfully following the SDU in response to which thenon-acknowledgement was transmitted; and means for transmitting, by thesource base station, the subsequent SDUs to the target base station. 37.The wireless communications apparatus of claim 36, further comprisingmeans for receiving the handover command related to the mobile device.38. The wireless communications apparatus of claim 36, furthercomprising means for processing the last SDU received in-order.
 39. Acomputer program product, comprising: a non-transitory computer-readablemedium comprising: code for causing at least one computer to receive, bya source base station, a handover command related to a mobile device fortransferring communications to a target base station; code for causingthe at least one computer to determine, by the source base station, asequence index of a first missing service data unit (SDU) following alast service data unit (SDU) received in-order from the mobile device;code for causing the at least one computer to transmit, by the sourcebase station, the sequence index to the target base station in responseto the handover command; code for causing the at least one computer totransmit, by the source base station, a non-acknowledgement in responseto receiving one or more SDUs indexed following the sequence index ofthe last SDU received in-order from the mobile device; and code forcausing the at least one computer to transmit, by the source basestation and to the target base station, successfully received SDUsindexed sequentially following the SDUs in response to which thenon-acknowledgement is transmitted.